PRINEVILLE -- With the plunge of a giant plastic "Like" button, Facebook's Prineville data center was christened this afternoon with an opening distinctive to the social networking powerhouse.

By opening up the 150,000-square-foot concrete fortress that stores the updates, photos, videos, "Likes," and "Dislikes," of millions of Facebook users to tours, Facebook officials put an exclamation point on last week's vow to share the technology that built the place.

Officials showed off the multimillion-dollar state-of-the-art structure that they say uses 40 percent less energy than comparable facilities. Nevertheless, Facebook officials still fielded questions about the company's controversial use of PacifiCorp electricity, which is derived mostly from coal.

View full sizeFaith Cathcart/The OregonianThe new Prineville center breaks with data center convention by forgoing air conditioning, relying on design features and Central Oregon's climate to keep the powerful servers cool inside.

The data center will employ about 40 people, from computer server technicians to security guards. The full time jobs offer a sliver of economic hope for Crook County, which has seen its jobless rate hover between 17 percent to 20 percent.

Before Zuckerberg arrived, two top Facebook officials led tours and answered reporters' questions: Jonathan Heiliger, vice president of technical operations, and Tom Furlong, director of site operations.

The tour offered a glimpse of the data center's second-level "evaporative cooling system," the multi-layer method of transforming central Oregon air of all temperatures into a target of 80.6 degrees Fahrenheit with 65 percent relative humidity.

View full sizeFaith Cathcart/The OregonianThousands of filters fill the filter room from floor to ceiling at Facebook's new Prineville data center.

The air is routed through four elongated rooms that clean and cool it. One room is covered with an estimated 1,000 air filters similar to those found in home ventilation systems. Facebook officials acknowledged it would be a chore to change the filters.

A constant one-direction flow sends the air down to the data center's ground level, where thousands of computer servers, arrayed in dozens of rows, handle the data for about half of Facebook's 500 million users. However, at any one time, as Facebook's server capacity changes, all 500 million could be served in Prineville.

Another 150,000-square-foot portion of the Prineville center will open next door in the last quarter of this year, next to the existing center on the 127-acre site that sits on a bluff above town. "We have the ability to expand on this site," Heiliger said, though "we have no plans to do so at this time."

"That's something we're looking at," he said, "and we're really looking at it as, 'What is the best way to service our users?'"

Heiliger and Furlong would not comment on the cost of the Prineville Data Center, saying the information was proprietary. The privately held company's filings with Crook County initially valued the project at $200 million, which has doubled in scale since then.

Heiliger noted that Facebook had chosen to not purchase cleaner electricity credits from PacifiCorp's Blue Sky program. The symbolic move had been considered in the face of criticism from Greenpeace and other environmentalists for purchasing power from a PacifiCorp, which gets much of its energy from coal

"We're very focused on investing our dollars in improving efficiency," he said, saying that the company's money would be better spent in that manner and sharing advances with competitors and others.

"If even a fraction of them adopt our technologies, that would be far more effective," than purchasing alternative energy credits, he said.

On the other hand, an array of solar panels sits along one side of the building, an addition decided on only in December, Furlong said. The power generated by the panels is expected to supply sufficient electricity for the data center's offices.